This invention relates to a freeze preventing valve which can prevent itself from freezing even if the valve is used in a cold climate.
A room heater for a Diesel locomotive which travels during cold weather, for example, adopts in general a steam heater in view of structural and economical points. In this structure, valves for exhausting water from condensed steam are mounted at predetermined intervals at suitable positions along a steam feed pipe. A valve of this type is heretofore constructed, as shown in FIG. 1, to have a valve housing 2 connected to a steam feed pipe 1, an exhaust port 3 formed at the lower part of the housing 2, a valve element 4 disposed in the exhaust port 3 for opening or closing the exhaust port 3, a guide rod 5 for elevationally movably supporting the shaft 4a of the valve element 4, a valve body 6 for holding the rod 5 at the top thereof, and stainless bellows 7 disposed between the collar 5a of the rod 5 and the valve element 4. When the interior of the housing 2 is maintained by the stream at a high temperature, gas in the bellows 7 is heated and expanded to cause the bellows 7 to be elongated as shown in FIG. 1, thereby moving downwardly the valve element 4 to automatically close the exhaust port 3. Conversely when the steam is partly cooled to produce condensed water, which then flows into the housing 2 to thereby cool the bellows 7 through the pipe 1, the bellows 7 are contracted to move upwardly the valve element 4, with the result that the valve element 7 automatically opens the exhaust port 3. In this manner, the condensed water is naturally exhausted externally from the exhaust port 3 through a plurality of holes 6a perforated at the wall of the valve body 6.
Since the bellows 7 for automatically elevationally moving the valve element 4 upwardly or downwardly due to the temperature difference is, however, constructed to fill and seal the gas therein to be elongated as described above, the bellows 7 are affected by the influence of the fatigue of repeated elongations and contractions for a long period of time to become finely cracked, causing a gas leakage or improper opening or closing of the valve. Thus, the condensed water is concentrated in the valve housing in winter, the valve itself is thus frozen, and the valve housing is then damaged. Therefore, in order to remedy against the freeze of the valve with the condensed water, a preliminary valve 8 is opened to discharge the condensed water, or the valve body is formed in a lateral configuration. However, sufficient effect to overcome the above-described drawbacks cannot yet be achieved. To prevent the freeze of the valve of this type, it is necessary to check, maintain, and replace the bellows, and to provide a remedy of preventing the damage of the bellows themselves, i.e., the improvement of the durability in period and the reduction in the manufacturing cost.